Posted by lindsay on Saturday, May 18, 2013 at 7:41pm.
8cos^2X - 2 = 0 8cos^2x = 2 cos^2x = 2/8 = 0.25 cosx = sqrt(0.25) = 0.5 Xr = 60o = Reference angle. X-Xr = 180 x-60 = 180 X = 180+60 = 240o.